IEC 61131-3: The Abstract Factory Pattern

If instances of a function block have to be created, the exact type of the function block should be known before compiling. Properties of an application can hardly be expanded by this fixed assignment. For example, this will be the case when the function block is located in a library and the access to the source code is thus not possible. The instance variable is constrained by a specific type. A class factory can help to break these stiff structures.

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IEC 61131-3: Object composition with the help of interfaces

While the notion of inheritance is used readily and frequently, interfaces are rather rarely applied. However, interfaces provide a number of benefits, which increase flexibility of the PLC programs and improve maintenance. The following post will introduce the possibilities of interfaces relating to the IEC 61131-3 standard.

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